Staff

Abstract:
Reproducing the advanced complexity of native tissue by means of the 3D multi-functional construct is a promising tissue engineering approach to osteochondral tissue regeneration. In this study, we present a porous 3D construct composed of three zones responsible for the regeneration of non-calcified cartilage, calcified cartilage and subchondral bone. These three zones of the hybrid were composed of modified biopolymers: (i) alginate (Alg) reinforced by short polylactide (PLA) fibres, (ii) alginate and gelatine methacrylate (GelMA) combined with ß-tricalcium phosphate particles (TCP), (iii) 3D printed polycaprolactone scaffold subsequently modified with the use of an innovative solvent treatment method based on acetone and ultrasound stimulation, respectively. Combining the advanced deposition systems based on: (i) 3D printing coupled with a spray crosslinking system, (ii) an innovative deposition system based on a coaxial-needle extruder, (iii) fused deposition modelling (FDM) connected with post-fabrication treatment, allows us to fabricate the triphasic construct that emulates the structure and properties of the native osteochondral tissue. The aim of the study was to investigate the mechanical properties of the fabricated hybrid and its individual zones. Our results demonstrate the load-bearing capabilities of TC, but nevertheless it should be implanted below the surface line of host cartilage to protect it from strong stresses, at the same time allowing native host tissues to grow into it.

Keywords:
Triphasic scaffold, Osteochondral tissue engineering, Mechanical properties, Hydrogel with nanofillers, Modified PCL

Abstract:
One promising strategy to reconstruct bone defects relies on 3D printed porous structures. In spite of several studies having been carried out to fabricate controlled, interconnected porous constructs, the control over surface features at, or below, the microscopic scale remains elusive for 3D polymeric scaffolds. In this study, we developed and refined a methodology which can be applied to homogeneously and reproducibly modify the surface of polymeric 3D printed scaffolds. We have demonstrated that the combination of a polymer solvent and the utilization of ultrasound was essential for achieving appropriate surface modification without damaging the structural integrity of the construct. The modification created on the scaffold profoundly affected the macroscopic and microscopic properties of the scaffold with an increased roughness, greater surface area, and reduced hydrophobicity. Furthermore, to assess the performance of such materials in bone tissue engineering, human mesenchymal stem cells (hMSC) were cultured in vitro on the scaffolds for up to 7 days. Our results demonstrate a stronger commitment toward early osteogenic differentiation of hMSC. Finally, we demonstrated that the increased in the specific surface area of the scaffold did not necessarily correlate with improved adsorption of protein and that other factors, such as surface chemistry and hydrophilicity, may also play a major role.

Keywords:
surface modification, solvent treatment, polycaprolactone, BMP-2 adsorption

Abstract:
One promising strategy to reconstruct osteochondral defects relies on 3D bioprinted three-zonal structures comprised of hyaline cartilage, calcified cartilage, and subchondral bone. So far, several studies have pursued the regeneration of either hyaline cartilage or bone in vitro while—despite its key role in the osteochondral region—only few of them have targeted the calcified layer. In this work, we present a 3D biomimetic hydrogel scaffold containing β-tricalcium phosphate (TCP) for engineering calcified cartilage through a co-axial needle system implemented in extrusion-based bioprinting process. After a thorough bioink optimization, we showed that 0.5% w/v TCP is the optimal concentration forming stable scaffolds with high shape fidelity and endowed with biological properties relevant for the development of calcified cartilage. In particular, we investigate the effect induced by ceramic nano-particles over the differentiation capacity of bioprinted bone marrow-derived human mesenchymal stem cells in hydrogel scaffolds cultured up to 21 d in chondrogenic media. To confirm the potential of the presented approach to generate a functional in vitro model of calcified cartilage tissue, we evaluated quantitatively gene expression of relevant chondrogenic (COL1, COL2, COL10A1, ACAN) and osteogenic (ALPL, BGLAP) gene markers by means of RT-qPCR and qualitatively by means of fluorescence immunocytochemistry.

Keywords:
alginate, gelatin methacrylate, ß-tricalcium phosphate TCP, bioprinting, coaxial needle, calcified cartilage

Abstract:
In this paper, the effect of the presence of L929 fibroblast cells and a cyclic load application on the kinetics of the degradation of amorphous PLGA films was examined. Complex micro and nano morphological, mechanical and physico-chemical studies were performed to assess the degradation of the tested material. For this purpose, molecular weight, glass transition temperature, specimen morphology (SEM, μCT) and topography (AFM) as well as the stiffness of the material were measured. The study showed that the presence of living cells along with a mechanical load accelerates the PLGA degradation in comparison to the degradation occurring in acellular media: PBS and DMEM. The drop in molecular weight observed was accompanied by a distinct increase in the tensile modulus and surface roughness, especially in the case of the film degradation in the presence of cells. The suspected cause of the rise in stiffness during the degradation of PLGA films is a reduction in the molecular mobility of the distinctive superficial layer resulting from severe structural changes caused by the surface degradation. In conclusion, all the micro and nanoscale properties of amorphous PLGA considered in the study are sensitive to the presence of L929 cells, as well as to a cyclic load applied during the degradation process.

Keywords:
L929, aliphatic polyester, stiffness rise

Abstract:
In this study, we present an innovative strategy to reinforce 3D-printed hydrogel constructs for cartilage tissue engineering by formulating composite bioinks containing alginate and short sub-micron polylactide (PLA) fibers. We demonstrate that Young's modulus obtained for pristine alginate constructs (6.9 ± 1.7 kPa) can be increased threefold (up to 25.1 ± 3.8 kPa) with the addition of PLA short fibers. Furthermore, to assess the performance of such materials in cartilage tissue engineering, we loaded the bioinks with human chondrocytes and cultured in vitro the bioprinted constructs for up to 14 days. Live/dead assays at day 0, 3, 7 and 14 of in vitro culture showed that human chondrocytes were retained and highly viable (∼80%) within the 3D deposited hydrogel filaments, thus confirming that the fabricated composites materials represent a valid solution for tissue engineering applications. Finally, we show that the embedded chondrocytes during all the in vitro culture maintain a round morphology, a key parameter for a proper deposition of neocartilage extracellular matrix.

Keywords:
alginate, PLA, short fibers, hydrogel reinforcement, chondrocytes

Abstract:
The aim of this study was to change the surface of sodium alginate hydrogel by electrostatic binding of poly-l-lysine (PLL) in order to provide more advantageous conditions for connective tissue development. Its impact on L929 mouse fibroblast adhesion, morphology and viability was investigated. Analysis of the material microstructure has shown that performed modification increased surface roughness. It also altered the swelling properties of alginate hydrogel, resulting in less rapid water absorption. Mouse fibroblasts seeded on regular alginate and alginate modified with PLL exhibited different behaviour. The presence of PLL turned out to promote cell adhesion and F-actin spreading, resulting in significantly increased number of viable cells 96 h after seeding.

Keywords:
Alginate, Poly-l-lysine, Electrolyte membranes, Cell adhesion

Abstract:
The progress in the treatment of chronic diseases of civilization that occurred in recent years, led to a significant prolongation of median survival time of the developed countries societies. Organ transplantation has revolutionized medicine as it became possible to replace an irreversibly diseased organ. However, at the moment we can observe a significant shortage of organs for transplantation, which forces doctors to accept those coming from more and more expanding criteria donors. No doubt, the number of donors, at best, will certainly not grow. Tissue engineering and regenerative medicine methods are extremely promising, in particular bioprinting of tissues and organs, which begun to develop at the beginning of the XXI century. Article highlights possible future direction of organ transplantation.